Federal regulators decided not to open an inquiry on the ignitions of Chevrolet Cobalts and other cars even after their own investigators reported in 2007 that they knew of four fatal crashes, 29 complaints and 14 other reports showing a problem that disabled the cars' air bags, according to a memo released by a House subcommittee on Sunday.

The memo also revealed that General Motors approved the faulty design of the switch in 2002 even though the company that made the part, Delphi, warned the automaker that the switch did not meet specifications. This followed a warning the year before - when the Saturn Ion was being developed - but GM said that "a design change had solved the problem," according to the memo.

The striking new details in the memo bolster the contention that both GM and the National Highway Traffic Safety Administration, more than previously acknowledged, ignored or dismissed warnings for more than a decade about a faulty ignition switch that, if bumped, could turn off, shutting down the engine and disabling the air bags. General Motors has recalled nearly 2.6 million cars and has linked 13 deaths to the defect.

Late Sunday, the safety agency said in a statement, "As we have stated previously, the agency reviewed data from a number of sources in 2007, but the data we had available at the time did not warrant a formal investigation."

In a statement, General Motors said, "We deeply regret the events that led to the recall. We are fully cooperating with NHTSA and the Congress and we welcome the opportunity to help both have a full understanding of the facts."

House hearing

A House subcommittee, which gathered more than 200,000 pages of documents from GM and 6,000 pages from the agency, will hold a hearing Tuesday. Mary Barra, General Motors' chief executive, and David Friedman, the acting administrator of the safety agency, are scheduled to testify. Both are also scheduled to testify before a Senate panel on Wednesday.

The most damaging finding in the memo concerned the four fatal crashes that went unheeded by regulators.

In a presentation dated Nov. 17, 2007, the safety agency's investigators reported to its Office of Defects Investigation on the fatal crashes, as well as a broad range of complaints and other reports about cars shutting off.

"The panel did not identify any discernible trend and decided not to pursue a more formal investigation," the House memo said.

The findings reinforce an analysis by the New York Times published March 8 that found the agency had received more than 260 complaints about cars in the recall, citing potentially dangerous shutdowns.

Recall expanded

On Friday, the recall was expanded to nearly 2.6 million cars, to cover vehicles that might have been repaired with defective switches.

The Times reviewed almost 8,000 complaints about the recalled models to look for examples when drivers may have been affected by a faulty ignition.

Neither of the two people scheduled to testify, Barra and Friedman, was in the job during most of the period in question, so the testimony might not establish how the critical decisions were made.